(3G) Civil War in US?

Interesting article from Telecom Magazine

In US Sprint Nextel and Verizon Wireless fly the flag for CDMA2000, while AT&T and T-Mobile USA spearhead the W-CDMA charge.

So far, CDMA2000 clearly has taken the high ground. Verizon laid claim to about 60.7 million CDMA2000 customers by the end of March 2007, while Sprint Nextel said it had captured 53.6 million. The W-CDMA operators, by comparison, could muster just 2.5 million customers between them.

The CDMA Development Group (CDG), which lobbies for CDMA2000, attributes this gulf to a technology lead. CDMA2000 operators, it notes, have deployed enhancements like EV-DO Revision A, which can deliver speeds of up to 3 Mbps for VoIP and multimedia applications. W-CDMA, in stark contrast, is still unavailable in many parts of the U.S. Even where it has been deployed, it typically is capable of a far less impressive 384 kbps.

W-CDMA, however, is definitely on the march. AT&T and T-Mobile USA are planning rollouts using HSDPA, a W-CDMA enhancement that offers speeds of up to 3.6 Mbps. More importantly, while W-CDMA’s customer base of 2.5 million appears low when judged alongside CDMA2000, it has grown from just 350,000 late last year.

“AT&T uses a higher frequency [than its CDMA2000 competitors], which is a disadvantage,” explains Allen Nogee, a principal analyst with In-Stat.
Generally, U.S. operators have deployed CDMA2000 using spectrum in the 800 MHz or 1900 MHz bands, while AT&T is rolling out W-CDMA using 2100 MHz spectrum. The lower frequencies have better propagation characteristics, allowing CDMA2000 operators to serve a wider area using fewer base stations.

“AT&T is also in a transitional phase,” Nogee adds. “Although it can advertise its new HSDPA network, that network has not been rolled out everywhere yet.”

Meanwhile, T-Mobile USA, the fourth largest operator in the U.S., plans to launch a W-CDMA service using the 2110 MHz to 2155 MHz spectrum it purchased in last year’s auction for advanced wireless services. Although it did not respond to requests for an interview, T-Mobile USA previously issued a statement on its 3G intentions in which it says the company will transition to a next-generation technology, which may include W-CDMA/UMTS with HSDPA, in the next two-to-three year timeframe.

And finally we cannot have a discussion without looking at the future (4G?):

Although W-CDMA is still in its early days in the United States, operators already are thinking about the next generation of mobile technology.
While a 4G standard is not yet defined, marketing departments are applying the label to some technologies already in development.

For W-CDMA operators such as AT&T and T-Mobile USA, the technology typically viewed as 4G is called long-term evolution, or LTE. It represents the destination on their journey through upgrades to HSPA, but will use a different air interface called OFDMA and require more work. Theoretically LTE will deliver downlink speeds of 100 Mbps and uplink speeds of 50 Mbps.

CDMA2000 operators also have 4G in their sights in the shape of EV-DO Revision C. Like LTE, Revision C promises vast improvements over the current crop of wireless standards. Allen Nogee, a principal analyst with In-Stat, thinks both LTE and Revision C could see commercial deployment by 2010.

In the meantime, Sprint Nextel has been vocal about another 4G technology. Last year, it earmarked US$2.5 bn for investment in a nationwide deployment of WiMAX, using 2.5 GHz spectrum it already owned. WiMAX proponents have made some bullish claims about its capability (promising up to 70 Mbps on the downlink), but the technology has not evolved from other standards—unlike LTE and Revision C—and will lack any scale economies when it is launched next year.

Chris Pearson, president of 3G Americas (a lobby group for W-CDMA), is unconvinced by the WiMAX business case. “It’s a wild card. In our view, most subscribers will be using W-CDMA and EV-DO for years to come.”

OFDM and OFDMA: The Difference

I was curious as to why IEEE 802.16d (fixed service) uses Orthogonal Frequency Division Multiplexing (OFDM). IEEE 802.16e (mobile) uses Orthogonal Frequency Division Multiple Access (OFDMA). So, what’s the difference between the two, and why is there a difference?

Lets first look at FDM:

In FDM system, signals from multiple transmitters are transmitted simultaneously (at the same time slot) over multiple frequencies. Each frequency range (sub-carrier) is modulated separately by different data stream and a spacing (guard band) is placed between sub-carriers to avoid signal overlap.

OFDM is sometimes referred to as discrete multi-tone modulation because, instead of a single carrier being modulated, a large number of evenly spaced subcarriers are modulated using some m-ary of QAM. This is a spread-spectrum technique that increases the efficiency of data communications by increasing data throughput because there are more carriers to modulate. In addition, problems with multi-path signal cancellation and spectral interference are greatly reduced by selectively modulating the “clear” carriers or ignoring carriers with high bit-rate errors.

Like FDM, OFDM also uses multiple sub-carriers but the sub-carriers are closely spaced to each other without causing interference, removing guard bands between adjacent sub-carriers. This is possible because the frequencies (sub-carriers) are orthogonal, meaning the peak of one sub-carrier coincides with the null of an adjacent sub-carrier.

In an OFDM system, a very high rate data stream is divided into multiple parallel low rate data streams. Each smaller data stream is then mapped to individual data sub-carrier and modulated using some sorts of PSK (Phase Shift Keying) or QAM (Quadrature Amplitude Modulation). i.e. BPSK, QPSK, 16-QAM, 64-QAM.

OFDM needs less bandwidth than FDM to carry the same amount of information which translates to higher spectral efficiency. Besides a high spectral efficiency, an OFDM system such as WiMAX is more resilient in NLOS environment. It can efficiently overcome interference and frequency-selective fading caused by multipath because equalizing is done on a subset of sub-carriers instead of a single broader carrier. The effect of ISI (Inter Symbol Interference) is suppressed by virtue of a longer symbol period of the parallel OFDM sub-carriers than a single carrier system and the use of a cyclic prefix (CP).

The OFDM spread-spectrum scheme is used for many broadly used applications, including digital TV broadcasting in Australia, Japan and Europe; digital audio broadcasting in Europe; Asynchronous Digital Subscriber Line (ADSL) modems and wireless networking worldwide (IEEE 802.11a/g).

Like OFDM, OFDMA employs multiple closely spaced sub-carriers, but the sub-carriers are divided into groups of sub-carriers. Each group is named a sub-channel. The sub-carriers that form a sub-channel need not be adjacent. In the downlink, a sub-channel may be intended for different receivers. In the uplink, a transmitter may be assigned one or more sub-channels.

Subchannelization defines sub-channels that can be allocated to subscriber stations (SSs) depending on their channel conditions and data requirements. Using subchannelization, within the same time slot a Mobile WiMAX Base Station (BS) can allocate more transmit power to user devices (SSs) with lower SNR (Signal-to-Noise Ratio), and less power to user devices with higher SNR. Subchannelization also enables the BS to allocate higher power to sub-channels assigned to indoor SSs resulting in better in-building coverage.

Subchannelization in the uplink can save a user device transmit power because it can concentrate power only on certain sub-channel(s) allocated to it. This power-saving feature is particularly useful for battery-powered user devices, the likely case in Mobile WiMAX.

The WiMAX forum established that, initially, OFDM-256 will be used for fixed-service 802.16d (2004). It is referred to as the OFDM 256 FFT Mode, which means there are 256 subcarriers available for use in a single channel. Multiple access on one channel is accomplished using TDMA. Alternatively, FDMA may be used.

On the other hand, OFDMA 128/512/1024/2048 FFT Modes have been proposed for IEEE 802.16e (mobile service). OFDMA 1024 FFT matches that of Korea’s WiBRO. OFDM 256 also is supported for compatibility with IEEE 802.16d (fixed, 2004).

IMT Advanced = 4G

In this story on Telecom TV, is says:

Working under a mandate to address "systems beyond 3G", the working party has now come up with a name for the future mobile systems. Thankfully, they are veering away from 4G and are calling it 'IMT-Advanced'.

A simple search on Google returned some useful information from Telecom ABC:

International Mobile Telecommunications - Advanced (IMT-Advanced) is a concept from the ITU for mobile communication systems with capabilities which go further than that of IMT-2000. IMT-Advanced was previously known as “systems beyond IMT-2000”.

It is foreseen that the development of IMT-2000 will reach a limit of around 30 Mbps. In the vision of the ITU, there may be a need for a new wireless access technology to be developed around the year 2010 capable of supporting even higher data rates with high mobility, which could be widely deployed around the year 2015 in some countries. The new capabilities of these IMT-Advanced systems are envisaged to handle a wide range of supported data rates according to economic and service demands in multi-user environments with target peak data rates of up to approximately 100 Mbit/s for high mobility such as mobile access and up to approximately 1 Gbit/s for low mobility such as nomadic/local wireless access.

To support this wide variety of services, it may be necessary for IMT-Advanced to have different radio interfaces and frequency bands for mobile access for highly mobile users and for new nomadic/local area wireless access.

Together with the introduction of the name IMT-Advanced, the ITU introduced the generic root name IMT. The generic root name IMT covers the capabilities of IMT-2000, including future development of IMT-2000, and IMT-Advanced.

Meanwhile a story in ChinaTechNews is suggesting that Datang Telecom has already written a Draft on 4G and is working on 3G&4G convergence. Cannot find much more on this right now.

For more on 4G technologies, either read this story on Network World or 3G4G website.

3G -> 3.9G

There seems to be confusion when people discuss terms like 3.5G, 3.75G so i decided to define them. I am sure people who have objections will comment.

Lets first start with 2G systems:

2G = GSM

2.5G = GPRS

2.75G = EDGE

Then moving onto 3G systems:

3G = WCDMA, R99 (i am not looking at other technologies but similar mapping will apply)
3.5G = HSDPA

3.75G = HSUPA

3.8G = HSPA+ (HSPA Enhancements)

3.85G = 'HSPA+' + MIMO
3.9G = LTE

4G = NOT WiMAX

More 4G and WiMax

In a recent article in EE Times, the author is stressing that "Mobile WiMax opportunities will be the next big growth engine for personal broadband and next-generation cell phone networking equipment vendors and for the communications industry in general". A good point raised though is that there are many people who have comitted to WiMax:

In US, global communications carriers like Sprint have announced plans to deploy large-scale mobile WiMax services by mid-2008. In some cases, entire countries have committed to WiMax as their fourth-generation standard of choice. Two such examples are Korea, with the early WiBro predecessor to mobile WiMax, and Taiwan, with the "M-Taiwan" national initiative.

What other thing the author is trying to stress is that WiMax is 4G but i do not agree.

Sony Ericsson is another high profile name that recently announced joining of WiMax forum. According to MacNN, no hardware updates or new products have been announced, but it's likely that Sony-Ericsson will begin to upgrade their products to take advantage of faster speeds.

According to another article in ARN today:

Unlike 3G, no specific standards spell out what a 4G service, network or technology is today. Analysts say these specifications are to come, but today "4G is more of a marketing idea," says Phil Redman, a research vice president at Gartner.

There is a mobile WiMAX standard -- the IEEE's 802.16e standard -- on which Sprint Nextel is basing its US$3 billion investment. But Redman says mobile WiMAX is not 4G, "although the WiMAX folks would love for that label to catch on."
Still, WiMAX and other technologies may be part of a forthcoming 4G specification. "There's no doubt that existing technologies like WiMax and other technologies such as [Orthogonal Frequency Division Multiple Access] and [multiple input multiple output] will be included in 4G," Redman says. "But no one technology will be 4G."

"These things tend to run in 10-year cycles," Redman says. "2G came out in 1995, 3G in 2004. There will not be a 4G standard before 2015."
In the meantime, a number of players have attempted to spell out what 4G should look like. The World Wireless Research Forum (WWRF) says 4G will run over an IP infrastructure, interoperate with Wi-Fi and WiMAX, and support fast speeds from 100Mbps to as high as 1Gbps.

It's also key that next-generation wireless includes QoS metrics and the ability to prioritize traffic, says Lisa Pierce, a vice president at consulting firm Forrester Research. "Lack of prioritization is preventing businesses from using current EV-DO services as their primary data connection."

WWRF expects 4G will be a collection of technologies and protocols, not just one single standard. That's similar to 3G, which today includes many technologies such as GSM and CDMA that meet specific criteria.

To help move the standards process along, WWRE -- whose members include Ericsson, Huawei Technologies and Motorola -- contributes to standards work done within groups such as the International Telecommunications Union (ITU), the group that defined 3G wireless specifications, and the IETF.

4G's predecessor, 3G wireless, is still taking off. The fourth-largest wireless-service provider, T-Mobile,launched its 3G network this year. So if 3G is just getting going, what does that mean for 4G?

Opinions on when 4G services might be available differ. The Next Generation Mobile Networks (NGMN) group says commercial services beyond 3G could launch as early as 2010. KPN Mobile, Orange, Sprint, T-Mobile International, Vodafone, China Mobile and NTT DoCoMo make up NGMN. The goal of the group, similar to the WWRF, is to work with standards bodies in developing next-generation specifications.

But if standards don't come before 2015, as Gartner's Redman predicts, true 4G services could come only after 2015.

Qualcomm, OFDM and 4G (17/05/07)

Qualcomm is the pioneer of next generation wireless technologies. To stregthen their position further, they have also bought over some smaller companies to give them access to all their IPR, etc. Yesterday i read an interview of Bill Davidson, senior vice president of investor relations and international marketing at Qualcomm and IDG news service. Here are some interesting points:

IDGNS: Is OFDM a new area of development for Qualcomm?
Davidson: If you go back to the beginning of Qualcomm, OFDM was considered a path instead of CDMA. The company ended up going down the CDMA route because CDMA was better able to handle all the things you want to do on a wide-area wireless network. We believe that to this day.

IDGNS: Are you planning any more acquisitions of companies with OFDM technology?
Davidson: In the last couple of years, our acquisition activity has stepped up. Flarion was clearly the largest deal of the last few years.

IDGNS: Do intellectual property rights play a big role in your acquisition strategy?
Davidson: They can and, clearly in the case of Flarion, there was a double benefit. First and foremost, we got the only team -- to this day -- to deploy a working mobile OFDM system. We also got the intellectual property rights that came along with the business. Our acquisitions are focused on accelerating time to market on a build-versus-buy decision and augmenting engineering resources more than we're out trying to grab patents.

IDGNS: What's driving all the interest in OFDM?
Davidson: We're seeing interest in OFDM because spectrum is becoming available in the 10MHz blocks and wider. From an efficiency standpoint, there's not really a benefit for OFDM over CDMA. But when you get into wider branches of spectrum, it can be a little less complex to implement.

IDGNS: But isn't 4G -- in which OFDM will play a big role -- all about newer, faster services?
Davidson: I think OFDM is really just a spectrum play. And frankly, we don't subscribe to the "4G" term. The applications that I've heard discussed aren't a whole lot different from what is being enabled over 3G today.

IDGNS: Isn't 4G supposed to be a lot faster than 3G?
Davidson: Many are talking about data rates that we don't even get on landline systems today. Yes, you can enable HDTV over these enormously wide pieces of spectrum. But what is the practical cost to the end-user?

IDGNS: So do we really need 4G?
Davidson: There is an existing roadmap within existing 3G technologies that provide the very same and, in most cases, better performance than some of the new technologies being proposed by other groups.

IDGNS: So WiMax and LTE aren't necessary?
Davidson: I look at LTE and UMB as being comparable; WiMax is not comparable to those technologies in terms of performance. There is a mistake in the premise that whatever comes along -- what people are calling 4G -- will be something that supplants the existing networks. We've been saying for several years that it will be about multiple airlinks existing in the market and making them work effectively together.

IDGNS: Let me come back to WiMax: Why isn't it comparable to LTE?
Davidson: Because its original legacy is borne out of the fixed environment, there are immediate engineering trade-offs and performance issues that you come up against. There is this concept of link budget, or how effective a technology is over the airlink. WiMax suffers from poor spectral efficiency because of its heritage as not being a mobile standard.

IDGNS: Do you see any intellectual property rights issues with 4G?
Davidson: We believe that our OFDM, OFDMA, and MIMO portfolio is among the strongest out there and clearly believe that it's applicable to any OFDM/OFDMA systems. Unfortunately, those who are supporting WiMax are trying to make it sound that the IP (intellectual property) picture with this technology is very clear and that it's going to be simple. The IP picture in 3G is much clearer today than what exists in WiMax. The number of companies claiming IP that can be contributed to WiMax is enormous.

IDGNS: Will Qualcomm be active in WiMax in any way?
Davidson: As we said several years back when many were trying to say that Wi-Fi would come and kill 3G, to the extent that our customers want the integration of Wi-Fi into our chipsets, we'll accommodate that. We've said the same about WiMax. We're being pragmatic and view that it will be in the market.

IDGNS:
Nokia CEO Olli-Pekka Kallasvuo said at the company's recent shareholders' meeting that the Finnish manufacturer can't give one company, Qualcomm, a chance to dictate rules for the whole industry. He said the issue is not Qualcomm versus Nokia but rather it's more about Qualcomm versus the rest of the industry. And your opinion?
Davidson: It's amusing to me that Nokia seems to think it's holding up the banner for the entire industry. If not for Qualcomm, there would be far fewer handset manufacturers for them to deal with as competitors and potential competitors. Our business model gives consumers a lot more choice so that Nokia can't dictate pricing into the market. Because we hold intellectual property, Nokia wants to paint us controlling the industry. We enable a lot of competition that causes them a lot of concern -- hence why we're being attacked by them.

The last point is amusing and i tend to agree with Qualcomm on this. Nokia has been dominating the market for long time and its about time other players get in the game.